It's hard for most NFL teams to consistently stay towards the top of their division, conference or whatever. And it can be just as hard to back up an outstanding regular season with another one the following year.

Such is parity at the NFL level. Last year's upstart team, poised to be a Super Bowl contender, can easily fall well short of expectations and wind up wondering just what went wrong. Case in point, all one has to do is look at the 2018 Jacksonville Jaguars, who went 5-11 a year after missing out on an AFC Conference Championship game victory by only a handful of plays.

So, which teams are in danger of some serious regression in 2019?

Granted, this is a prediction piece. There are plenty of factors that'll ultimately affect any team's chances between now and Week 1. Free agency will have a lot of say. So will April's NFL Draft.

For now, though, here are five who may fall well short of expectations this upcoming season.

Kansas City Chiefs — 2018 Record: 12-4

This might not be as severe a regression as the others, so let's start here. The Chiefs are coming off one of the most outstanding seasons in franchise history, led by 2018 MVP quarterback Patrick Mahomes.

Mahomes' meteoric rise should continue, for sure, but to expect another record-setting year from the young signal-caller might be a bit premature.

Enough of that, though. He should be fine. What could be problematic for Kansas City is the relatively low amount of cap space the team has heading into 2019 — $10,106,537 currently, according to Over the Cap. That's roughly enough to absorb the Chiefs' rookie class this season, but there won't be a lot of wiggle room to bring in some much-needed defensive talent.

Kansas City does have eight picks in this year's defense-heavy NFL Draft, including the No. 29 pick. That should help. But those financial considerations forced the Chiefs to make some tough moves, including having to move on from veteran edge rusher Justin Houston, who has a combined 18.5 sacks from a year ago.

While rookie reinforcements should help, one shouldn't automatically expect the Chiefs' defense to make leaps-and-bounds improvements this season, even with a new defensive coordinator, Steve Spagnulo.

2019 will likely be another season in which the Chiefs' offense has to carry the load again, but it will be much more difficult to take the league by storm compared to last year.

New Orleans Saints — 2018 Record: 13-3

The Saints have come close to reaching the Super Bowl in back-to-back years, only to fall short in heartbreaking fashion. Unlike the Chiefs, however, there are far more pressing questions that could put New Orleans' immediate future in doubt.

There's the obvious, of course: quarterback Drew Brees' age. He just turned 40 years old and will be coming off a season in which he tossed the fewest passing yards (3,992) since his 2005 efforts with the San Diego Chargers. That's still an amazing number, but Brees is playing with time, and the drop-off from an elite signal-caller to being barely effective under center can be quick. Just look at quarterback Peyton Manning's final years with the Denver Broncos as an example.

Yet the Saints' issues heading into 2019 go far beyond Brees. Outside of wide receiver Michael Thomas, Brees doesn't have a slew of bona fide pass-catching options. Tight end Ben Watson retired, and New Orleans doesn't have a lot of resources to replace him and address other areas of concern, which should included a banged-up offensive line.

Why not? The Saints also have just over $10 million in cap space and are armed with one pick (No. 62) in the first four rounds of the NFL Draft.

It's not an ideal situation to be in; replicating last year's impressive playoff run will be difficult to achieve.

Los Angeles Rams — 2018 Record: 13-3

After their offense was embarrassed, 13-3, by the Patriots in Super Bowl LII, one has to wonder if the Rams are destined for one of those proverbial Super Bowl “hangovers.”

Perhaps, and we'll have to see how well head coach Sean McVay handles that. The same goes with concerns surrounding running back Todd Gurley, who was the linchpin of McVay's offense.

Los Angeles went “all in” last season, which explains the numerous free-agent pickups and trades the organization made while quarterback Jared Goff continued on his rookie contract. That still leaves the Rams in pretty good shape, cap-wise, with just a shade under $30 million currently available. Yet there are more than a few pressing free-agent decisions on the table for L.A., including defensive tackle Ndamukong Suh, edge rusher Dante Fowler, offensive guard Rodger Saffold, and safety Lamarcus Joyner.

Re-signing all of those players will be difficult. Holding onto the top spot in the NFC West might be difficult, too.

Chicago Bears — 2018 Record: 12-4

Like the 2017 Jaguars, the 2018 Bears primarily used their defense to ride a trip into the postseason. Trading for edge rusher Khalil Mack sure worked out, didn't it? He alone could be an easy reason why Chicago's defense remains just as dominant in 2019.

Yet that defense is going to go through a lot of changes this year, which include having to absorb losing defensive coordinator Vic Fangio to the Denver Broncos' head coaching vacancy. That's huge: Fangio is considered one of the best defensive minds in NFL circles.

There's more than just Fangio, however. Defensive backs Adrian Amos and Bryce Callahan — two very effective members of a quality Bears secondary — hit the open market this offseason. We'll have to see how well the rest of Chicago's defense handles a pretty notable transition. Replacing possible player replacement could be tough, though: The Bears are without NFL Draft picks in Rounds 1 and 2.

But the Bears make this list of possible regressors for another reason, specifically similar to the one the Jaguars experienced last year. ‘

Defensively dominant teams have a difficult time replicating success on a year-to-year basis. Jacksonville is a prime example. The Super Bowl-winning Broncos from 2015 fell to 9-7 a year later, then 5-11 the next season. Even the Baltimore Ravens' 2000 squad — often viewed as the best defensive team this century — became a sub-.500 team within two seasons after their Super Bowl win.

Maintaining defensive continuity is extremely difficult, which puts a high point of emphasis on finding a quarterback (the game's most important position) capable of carrying a team through those defensive ebbs and flows.

Is Mitchell Trubisky going to take that next step in his evolution?

New England Patriots — 2018 Record: 11-5

Okay, so this gets said every year: “This is the season when we finally see the Patriots' dynasty come to a close.”

Then it's proven wrong, again.

Credit New England for proving any doubters wrong. Only fools bet against the Pats until they're actually out, and recent history tells you that's a bad bet anyway.

Let's assume, though, that eventual regression does take place this year. Why would that be the case? Sure, there's going to be the always-present talk of future Hall of Fame quarterback Tom Brady playing well into his 40s, and Father Time remains undefeated. So, that's a possibility. The same goes with an uncertain future surrounding tight end Rob Gronkowski.

Yet there are practical reasons for a possible New England regression in 2019, too. It's going to be tough to replace edge rusher Trey Flowers, who is one of the league's most underappreciated pass-rushers, if he winds up departing on the free-agent market. Defensive tackles Danny Shelton and Malcolm Brown are quality pieces hitting free agency. Adding veteran Michael Bennett helps alleviate that, though.

The good news is New England isn't in salary cap hell at all, but one should expect at least one of those players to be elsewhere in 2019.

Based on all we know about head coach Bill Belichick, he'll end up turning all 11 of the Pats' 2019 NFL Draft picks into gold-standard players, proving again why New England's dynasty refuses to go away and making us all fools for thinking “this is the year they'll regress.”